Wireless receiving improvement.



G. W. PICKARD.

WIRELESS RECElVlNG IMPROVEMENT.

APPLICATION FILED AUG.1. I9I0.

Patented Oct. 12, 1915.

3 SHEETS-SHEET 1 Atty COLUMBIA PLANOGRAPH c0., WASHINGTON. D. c.

G. W. PICKARD.

WIRELESS RECEIVING IMPROVEMENT.

APPLICATION FILED 1ue. 1.1910.

1,156,625." Patented 001.12, 1915.

3 SHEETS-SHEET 2.

1 Inventor:

2% mm Atty COLUMBIA PLANOGRAPH co., WASHINGTON. 0. cu-

G. W.' PICKARD.

WIRELESS RECEIVING IMPROVEMENT.

APPLICATION FILED AUG-l. 1910.

Patented Oct. 12, 1915.

3 SHEETS-SHEET 3- v enter: G'menZea/ V1 r w'kanZ Atty UNITED ES PATENTorr on.

f GRE NLnAR wHrrTmariciKAR-n; or A' RSBURY, MASSACHUSETTS, AsSIeNoR-ToWIRELESS SPECIALTY APPARATUS COMPANY, or NEW YORK, N. Y.; A coRr'o'RATIoN, ornnw YORK.

WIRELESS RECEIVING IMPROVEMENT.

To all whom z'tmdy concern: I

Be it. known that I, GREnNLEAr WHITTIER PICKARD, a citizen of the UnitedStates of America, and a resident 'of ,Amesbury, Massachusetts, haveinvented certain new and useful i/Vireless Receiving Improvements, theprinciples of which are Set forth in thefollowing specification andaccomr.

panying drawing, which disclose the form of the invention whiohI nowconsider to be the best ofthe various forms in which the principles ofthe invention may be embodied.

This invention relates to improvements in receiving messages and signalsby wireless telegraphy andtelephony.

v The principal ob ect is to increase the'eifi,

tact microphone Fig. 5 a thermal-wire con-.

trolled multiple-contaot or carbon button microphone, Fig. 6 an.electromagnetically controlled multiple contact or carbon buttonmicrophone; and Figs. 7and 8 are diagrams showing-the adaptation as awireless detector (in place of rectifier D of Fig. 1)

of. such microphonic device structures or comb nations as those of Figs.26.

-In Fig. 1, A may be any suitable antenna, which be grounded at G, andconnected 7 with the receiving. apparatus by any usual oscillation.transformer asT. If the second ary oscillation circuit, as the circuitthrough w 1 the transformer secondary and the condenser G, is to betuned to antenna A, then the rectifying detector 1),; (one'of mywellknown good-contact devices'wherein one or both of the contactmembers possesses recti-' fying power) is connected in shunt to thetuned circuit, as shown. It has been customary to connect; acrosscondenser C (which is in series with D a-telephone receiver, to beoperated by the direct current pulses furnished from the oscillatorycur- Specificationof Letters Patent. 7 Patented O t. 1915 Applicationfiled Au ust 1, 1910. Serial 115.574,?78. I

rents in the tuned circuit, by means of the rectifier D; the condenser Cbeing used to provlde a path through D for the oscillations, withoutshoit circuiting the telephone 7 receiver connected across C and thelocal Source B being such as to increase the rectifying efiiciency of D,inaccordance with the lnvention of my Patent 912,613, "but not tofurnish energy for the operation, of the re-i ceiving telephone. Thishas been very satis- I factory indeed for the commercial'business of thepast and'up to the present; but the present invention has for its resultto increase the ultimateefiici'ency thirty orforty times or more,andfurthermore the former arrangement, practically limited to the use ofthe telephone receiver, has certain disad vantages, among which is thefact that the telephone mustnalways' be at the operators ears if anybusiness is to be done. One reason why the telephone alone has been usedwithvmy rectifier detector isthat there was no other instrument whichwas efficient enough to be operated by the rectified ourrents underusua-l and general commercial conditions. y c

. In accordance with this. invention the rectified currents areamplified before being led to a telephone receiver, and preferably, theyare amplified so that they havesuffi cient. strength. to operate acontrolling other than a telephone and constituting a switch for anydesired translatingldevice telegraphic receiving instrument, suchvas.an

ordinary Morse sounder, a call-bell, a signaling la1np,.etc. I havefound, however, that the mere amplification is not adequate, of itself,to satisfactorily,accomplish the operation of suchcontrolling switch, onaccount of the. fact that the pulsatory character of the rectifiedcurrents is carried throughtheprocess of amplification, and that theinertia of the controlling switch will not permit its satisfactoryoperation by such pulsatory currents. In accordance with the invention,therefore, the pulsatory currents arechanged to currents constitutingdirect makes and breaks corresponding in duration to the duration of thesignals; this being done between the steps of rectification and' ofoperating the controlling switch. First, insteadofconnectin a telephonereceiver across condenser C Fig. 1), one of the devices of Figs. ,2 6 isconnected as shown at V F, T of Fig. 1, where coil and diaphragm Fconstitute the receiver element (similar to a telephone receiver) and Tis an adjustable electrode or contact of a suitable microphonetransmitter. I have found that with one of these devices, the rectifiedpulsatory current pulses from rectifier I.) can be amplified at leastthirty to forty times as the present upper limit so far accomplished byme. If now the ordinary telephone receiver heretofore used at V beplaced at IV, the amplification by 7*, F T permits an enormous increaseof the distance over which wireless telegraphy or telephony ispracticable. That is, not only are signals heretofore heard from distantstations, greatly in creased in intensity, but signals can be clearlyread from stations so far away that they had never been read before atsuch distance. But, in accordance with a preferred object of thisinvention, the amplified rectified pulses are to operate telegraphicinstruments other than telephones, z'. 6., instruments which do notrequire to be held to the operators ear in order to read the signals. Ifind,however, that even when the amplification is from thirty to fortytimes, as by the instruments of Figs.26, it is far below the strengthrequired to overcome the inertia of. a telegraphic instrument like aMorse sounder. For this reason, and for the stated purpose, it isdesirable to cut in atleast another amplifier, as W, T with preferablybut not necessarily another local source, as a cell of battery B like BIf a common local source is used for a plurality of amplifiers, or forall the receiving devices of Fig. 1, such source should be of very lowresistance, as a storage battery, to avoid cross fire or interference.Likewise any telephone receiver used in place of amplifier T should beof low resistance; or if a high resistance telephone be used, it shouldbe provided with a telephone transformer.

When the second amplifier T is employed, the reamplification will beabout a thousand, assuming that the first amplification is over thirty,and that the efiiciency of VV T is the same as that of T This may besuflicient in some cases, but it is preferable for general service, andwith the efficiency so far obtained with the devices of Figs. 2-6, toprovide at least a third amplifier, as V T", thus finally amplifying tothe cube of the amplification of a single device, as T On the sameassumption as before, the total effect will be an amplification of aboutthirty thousand. That will be sufficient for most cases, although yetmore amplifiers may be added in tandem, if desired, as for any spe cialservice.

The next step after sufiicient amplification is to change the characterof the amplified rectified currents from the pulsatory form to directmakes and breaks. I find that that can be very efficiently done bycutting in a vibrating-contact relay, at NV, C of the constructionstandard in telegraphic or signaling work. The operation of this is asfollows, assuming for the present, that IV, Q is to directly operate theultimate controlling switch, as it may do if desired. The pulsatoryamplified rectified currents received in winding V act to vibrate a reedor tongue R to and from its contact C against which, in the lack of suchcurrents, it is normally held in good contact by spring S. During thevibration of reed R, the tongue Q, will not be operated. That is becauseit is moved only by the average cur rent through its winding IV, andbecause its inertia causes it to resist the irregularities in thereducedcurrent through W, which irregularities are caused by the vibration of reed R. But as soon as the pulsatory current through IV ceases,spring S closes circuit through IV", and tongue or armature Q, uponbeing drawn to WV, makes a sound indicating the termination of thesignal, its sound indicating the commencement of the signal having beenmade when it receded from NV under the action of spring S when thevibration of reed R commenced. This action is precisely that of theordinary Morse sounder, except that the sounds indicating the beginningand end of the signal are inverted or reversed. Thus the device IV, Q,may be an ordinary Morse sounder or any other desired translating devicethe circuit of which is closed by reed R. But it is preferable that theMorse sounder or other translating device be located at and that thedevice IV, Q, interposed between and WV, be a simple Morse relay actingon its back contact, as shown, to invert the makes and breaks caused byreed B so that when reed R is not in vibration the contact 0 is open,and the sounder V not energized. There are two principal reasons forthis preference. First, a telegraph operator is accustomed to read thesignals by the characteristic up-and-down strokes of the sounder, andmight be bothered if these were reversed. Second, owing to therelatively large current required for the operation of the sounder,there is danger of the reed R sticking or welding if it is compelled todirectly operate the sounder or the switch for the ultimate translatingdevice.

Notwithstanding that the ultimate translating device cannot besatisfactorily operated by the mere amplification of the rectifiedpulses, such amplification is necessary, and it apparently cannot beeffectuated without some such microphonic devices as those of Figs. 2G.

Fig. 2 shows an efficient microphonic amplifierof what-I term thesingle-contact type, thatcontact being at T 3, corresponding to T Fig.1,and adjustable as indicated. The'winding W corresponds to? of Fig.

' 1, and the diaphragm F to F :of Fig.1. Contact member 3 is mounted ondiaphragm F u- Contact member T is mounted on the endof an adjustingscrew in arm 8 which arm is pivoted at 9. A regulating orcontact-controlling winding 2 is mounted concentrically with winding Wthe two windings being mounted on their respective spools and'located'in the common metallic container 1 to which diaphragm F is clamped, asshown, as in" an'ordin'arytelephone receiver; l ermanent magnet 5 isacommon magnet for both windings V and 2, and supports an adjustablepole-piece 6 which extends up through winding 2 into winding W' whereitis adjusted to' within the shortest possibledistance of pole-pieceetwhich is mounted on diaphragm F This construction'is: of great"importance in' respect of the efficiency of the device," in that it.constitutes'a magnetic circuit of extremely low resistance. I l

The circuit ofwinding 2 includes th'e'microphone'contact T 3,diaphragm-F battery B and device W one end of :winding 2 beingconnectedfto metal container 1 and hence to diaphragm F clamped totliatcontainer. The other end of winding 2 is connected to the cell ofbatteryv B Device may be another amplifier as in Fig. 1, or it may be atelephonereceiver. It is important that the contacts T 3 be of thehardest pos sible conducting material; such as platinum or even theknown harder materials wheneverthe greater expense is no'object; I havefound an alloy of osmium and irridium to be entirely satisfactoryfor-both T and 3.

" The mechanical adjustment to microphone action is effected lay-screw7,bearing against arm 8 in which contact T is mounted The extensionofar1n '8 to the right, as shown, permits-a very'close adjustment,butI have found that to be very inefiicient when compared with thatwhich can be additionally obtained vby varying the strength of the fieldof'magnet 5, as by rotating the permanent magnet 11' which is locatednear ma gnetf). The user will proceed 'as follows After the bestpossible mechanical adjustment by screw 7, magnet llisslowly rotated byhand, so that the slight resultingvariations of strength of the field ofmagneti5 will result in a Very slight additional adjustment of contactsT 3. The great improvement in the microphonic' action will bereadily observed bythe action of sounder WV Fig; 1.- This method of additionaladjustment is much more delicate than is possible bythe The action inFig; 2 is as follows: The flow of current through the-microphoneT 3 'andthrough regulating winding. 2 varies sition of contact 3 with respect tocontact T Theregulating windingQis soconnected in circuit thatanincrease of current flow tends to separate contacts T 3, and vice versa,consequently the resistanceof the mi crophonic contact is increased byan increase of current fiow,and this in turn automatically reduces thecurrent flow and the pull onupole-piece 4:. Consequently, if theadjustment of the microphonic contactisd-isturbed,.so as to cause avariation in current fioW, or (if fthe'currentvaries for any reason, theadjustment is automatically i estored. Thus, for example, iftheresistance of the contact is increased or the ."current flow isdecreased, the pull on pole-piece 4i and diaphragm F -is reduced .so'that contacts T 3 are in closer adjustment by a most minute degree. Thus=:theinitial adlustment is maintained andthe device ren dered more stablethan a'microphone lacking automatic regulation. This automatic brationor singing of the contacts,'as indicated bywa characteristic note in atele phone receiver in. circuit. This singing is objectionable becauseit interferes W1tl1 the clear reception of signals, and I have de vlseda slmple means of elim'matmgit, consisting of the adjustable resistance10 connectedin shunt to the contact-controlling winding 2. Wheneversinging follows the adjustment by 7 or 11, the operator simply variesresistance 10 until the singing stops.

In the amplifier of Fig. 3, the electromag' netic control of Fig. 2 isdispensed with, and control is automatically effected by thethermal-wire 13, of any fine high-resistance ma terial, such as atwo-mil. man'ganinwira-of say a couple of inches in length, andadjustedat 14 so as to-bestretched tightly for its operative position, thisbeing preferably a permanent adjustment. The resistance adjustment at 10is in shunt to wire 13, co1w responding with its shunt connection towinding 2 in Fig. 2, and is for the same purpose here as in allthefigures. The actionis as follows: Upon the initial adjustment tomicrophone contact by screw 7, current flows through T 3, and wire 13.If this current is excessive, i. e., if the microphone contact is of toolow resistance for maximum efficiency, then the action is as follows:The slight heating of wire 13 by the current and its consequent slightincrease in length allow diaphragm F (to which it is attached near thecenter thereof) and contact member 3 to fall away to such slight extentfrom contact T, as to in crease the resistance to such degree as toimprove the microphonic efiiciency. This increased separation of themicrophonic con tacts decreases the current flow, thus limiting theheating and expansion of the wire, and thereby prevents further increaseof contact-separation. This method of control is extremely efiicient,particularly when combined with the efficient magnetic circuit shown,and described with reference to Fig. 2. The control is so sensitive,with such an efficient magnetic circuit, that the approach of theoperators hand to the wire 13 will instantly cause a wide deflection ofthe pointer of a milliammeter included in series in the circuit. Butnotwithstanding this sensitiveness, the automatic adjustment is verystable, and is adequate for commercial service. But the wire 13preferably is to be shielded from the effects of outside temperature. Ifdesired, diaphragm F inthe case of the thermal-wire control, may bereplaced by a reed.

In the amplifier of Fig. 1, the control is electrostatic, being effectedby the metal ring or annulus 15. The location of this annulus is belowand at the shortest convenient distance from diaphragm F and theestablishment of a diiference of potential between the two, causes anelectrostatic attraction or pull on the diaphragm F which results in aslight downward flexing thereof, carrying contact 3 a very slightdistance in the direction away from contact T \Vhen contact at T 3 isestablished initially by adjustment of screw 7, current flows throughthe microphone and through the device W resulting in an increaseddifference of potential across NV, and hence across the annulus 15 anddiaphragm F This increase of potential effects an increase in theelectrostatic pull and hence causes an increase in the separation ofcontacts T 3 and consequently an improvement in the operation of themicrophone. At the same time, this increase in contact-separationdiminishes the current flow, and the potential, and therefore preventsfurther pull on diaphragm F by annulus 15.

In Figs. 5 and 6 are shown forms of multiple-point microphones, such ascarbon granule buttons 16.

In Fig. 5 the control is by thermaLwire l3, asin Fig. 3. The magnet 5,carrying pole-piece 6, is adjustable in container 1, as shown. Thecarbon granules 16 are held between dlaphragm F and rear electrode 17,the latter having a small central perforation 18 through which wire 13extends to its attachment to the center of the diaphragm F Theresistance-adjustment 10 is provided as in Figs. 2 and 3.

In Fig. 6 the control is electromagnetic as in Flg. 2, the constructionbeing otherwise like Fig. 5.

I have discovered also that the microphone structures of Figs. 2-6 makeexcellent detectors of hi 'h frequency oscillations for use in wireleste .egraphy and telephony. For example, Fig. 7 shows the detector Dconsisting of microphone T 3, controlled by the thermal-wire 13stretched taut at 14, the general construction being as in the precedingdrawings; the mechanical adjustment 7 being indicated only directly atthe contact T for simplicity. The microphone is connected between A andG as shown, directly in series in the antenna, this being the preferredconnection unless very sharp tuning is required. Contact 3 is mounted onreed R to which control-wire 13 is connected. The automatic controltakes this detector out of the ordinary class of microphonic detectors,(which are extremely erratic and 9 unreliable), on account of theresulting stability. The receiving device 1V may be the usual telephonereceiver or any other suitable device, such as the amplifier V of Fig.l, or even the Morse sounder IV of Fig. 1. Thus the entire organizationat the left of 7 Fig. 1, may be supplanted by that of Fig. 7, with theexception of V and that no amplifiers WV WV etc., Fig. 1 are absolutelyrequired. The operation consists in the variation, by microphonicdetector D of the current flow from battery B, with resultingintelligible signals at IV. Then an amplifier is used, that involves amodification of the general method of Fig. 1, which modificationconsists in amplifying the variations of the current in battery B whichare caused by the microphonic action of detector D Also, inasmuch as theresulting current flow in W lacks the pulsatory character of that fromdetector D of Fig. 1, there is no need, as there is in Fig. 1, for theinterposition of a vibrating contact relay 7*, C between the detectorand the ultimate receiving device, as W Fig. 7, or VV Fig. 1.

In Fig. 8 the thermal-wire 13 is itself the detector D connected betweenA and G as shown, directly in series in the antenna, and stretched tautat 14 and mechanically connected to reed R. In this case the detector isan amplifier in which the wire 13 is directly acted upon by theoscillations received by A, G, and the resulting microscopic motions of13 (causedby heating by the os- -cillations), are amplified, to operatea receiving device such for example, as the milliammeter W by means ofthe variations at microphone T 3 which are caused by the movements ofwire 13, the reed R and contact member 3 being allowed to pull away fromT by the elongation of wire 13 caused by its heating. The wire 13 has inaddition, its action as in Fig. 7, of regulating the microphone T 3,since it is in the local oircuit with the battery and microphone, andmay be provided with the shunt adjusting resistance 10 as in Fig. 7 andthe other figures. The result is that microphone T 3 is automaticallyadjusted and that the microscopic motions of wire 13 are amplified intothe considerable and observable motions of the indicatingneedle of themilliammeter V7 In- Figs. 7 and 8 there is not the need of amplifyingdevices as is the case with the Copies of this patent may be obtainedfor rectifier detector l) of Fig. 1, because in Figs. 7 and 8 the energyused to operate receiving device W is that of battery B,

which may be considerable, whereas in Fig. 1 the energy used to operateW is only that of the oscillations themselves, which requireamplification in order to permit the operation of any receiving deviceexcept such a sensitive instrument as a telephone receiver.

I claim:

In an amplifier, the combination with a microphone, of a regulatingmagnet therefor havingits coil in circuit therewith, and an adjustablemagnet in the vicinity of said regulating magnet for varying the fieldof the latter.

GREENLEAF WHITIIER PIGKARD.

Witnesses:

' EDWARD H. RoWELL, ROLAND BROWNLIE.

five cents each, by addressing the Commissioner of Patents.

Washington, D. C.

